Apoptosis or programmed cell death is important during embryonic development, metamorphosis, tissue renewal, hormone-induced tissue atrophy and many pathological conditions. In multi-cellular organisms, apoptosis ensures the elimination of superfluous cells including those that are generated in excess, have already completed their specific functions or are harmful to the whole organism. In reproductive tissues that are characterized by cyclic functional changes, massive cell death occurs under the control of hormonal signals. A growing body of evidence suggests that the intracellular xe2x80x9cdeath programxe2x80x9d activated during apoptosis is similar in different cell types and conserved during evolution.
Apoptosis involves two essential steps. The Bcl-2 family of proteins that consists of different anti- and pro-apoptotic members is important in the xe2x80x9cdecisionxe2x80x9d step of apoptosis. In contrast, the xe2x80x9cexecutionxe2x80x9d phase of apoptosis is mediated by the activation of caspases, cysteine proteases homologous to the C. elegans protease ced-3, that induce cell death via the proteolytic cleavage of substrates vital for cellular homeostasis. Bcl-2-related proteins act upstream from caspases in the cell death pathway and recent studies demonstrated that another C. elegans gene, ced-4, or its mammalian homolog Apaf-1 can bridge between Bcl-2/ced-9 family members and caspases.
The proto-oncogene Bcl-2 was originally isolated at the breakpoint of the t(14,18) chromosomal translocation associated with follicular B-cell lymphoma. Over-expression of Bcl-2 suppresses apoptosis induced by a variety of agents both in vitro and in vivo. Subsequent studies identified a family of Bcl-2-related proteins possessing several conserved BH (Bcl-2 homology) domains important for homo- or hetero-dimerization between family members. In addition, a C-terminal transmembrane region for membrane anchoring is also conserved in most members. Based on their differential roles in regulating apoptosis, the Bcl-2-related proteins can be separated into anti-apoptotic (Bcl-2, Bcl-xL, Mcl-1, Bcl-w and Bfl-1/A1) and pro-apoptotic members (Bax, BAD, Bak, Bik, Hrk and BID). Through hetero-dimerization, the balance between pro- and anti-apoptotic proteins presumably determines cell fate. The anti-apoptotic effect of Bcl-2 is not universal, however, because Bcl-2 over-expression is not effective in blocking Fas-mediated apoptosis and the apoptosis of auto-reactive thymocytes during negative selection. Recent identification of multiple Bcl-2-related proteins suggests that selective Bcl-2 members may act in a tissue- and dimerization-specific manner.
Bcl related genes are discussed in Yin et al. (1994) Nature 369:321-323; Chittenden et al. (1995) EMBO J. 14:5589-5596; and White (1996) Genes Dev.10:1-15.
Sequences of exemplary bcl-related genes may be accessed in Genbank. The human hrk gene has the accession no. U76376 and is described in Inohara et al. (1997) EMBO J. 16:1686-1694. The human bcl-w gene has the accession no. U59747 and is described in Gibson et al. (1996) Oncogene 13:665-675. Human A1 gene has the accession no. U29680, and is described in Karsan et al. (1996) Blood 87:3089-3096. The human Bak gene has the accession no. U23765, and is described in Chittenden et al. (1995) Nature 374:733-736. The human Bak-2 gene has the accession no. U16812, and is described in Kiefer et al. (1995) Nature 374:736-739. The human Bik gene has the accession no. U34584, and is described in Boyd et al. (1995) Oncogene 11:1921-1928. The human Bfl-1 gene has the accession no. U27467, and is described in Choi et al. (1995) Oncogene 11:1693-1698. The human bcl-2 gene has the accession no. M13995, and is described in Tsujimoto and Croce (1986) P.N.A.S. 83:5214-5218. The human Bax genes have the accession nos. L22475, L22474 and L22473, and are described in Oltvai et al. (1993) Cell 74:609-619. The EBV BHRF1 gene has the accession no. A22899, and is described in WO 9311267. The human mcl-1 gene is described in Kozopas et al. (1993) P.N.A.S. 90:3516-3520, and OMIM 159552.
The EST fragment, Genbank accession no. AA103989, contains partial sequence of the 5xe2x80x2 end of the mouse Bok gene.
Isolated nucleotide compositions and sequences are provided for Bok genes. The provided nucleic acids include splice variants encoding long forms of the protein, as well as short forms having a truncation that deletes all or a part of the BH3 domain. The short form of Bok and other related pro-apoptotic proteins may be naturally occurring or synthetic. These short forms induce cell killing without heterodimerization with antiapoptotic proteins.
The Bok nucleic acid compositions find use in identifying homologous or related genes; in producing compositions that modulate the expression or function of its encoded protein; for gene therapy; mapping functional regions of the protein; and in studying associated physiological pathways. In addition, modulation of the gene activity in vivo is used for prophylactic and therapeutic purposes, such as treatment of cancer and other proliferative disorders, identification of cell type based on expression, and the like.